Mower convertible into a tracked implement and vice versa

ABSTRACT

This invention relates to a mower and a tracked implement that convert from one to the other by coupling a mower unit or a tracked unit to a common drive unit. The drive unit is thus used in both products to provide cost savings in the purchase of the equipment. In the tracked unit, a cab for enclosing the operator&#39;s station is part of the tracked unit and gets mounted to the drive unit when the tracked unit is coupled to the drive unit. A pair of idlers rotate on pivot axes that are fixed relative to a pivotal idler support that carries the idlers. The pivot point for the idler support is chosen to prevent track elongation when the tracked unit climbs obstructions such as a curb. In the mower unit, a relatively heavy cutting deck is used and spring biased weight transfer arms transfer some of the deck weight to the mower frame.

TECHNICAL FIELD

This invention relates generally to the field of outdoor power equipmentand to a mower that is convertible to a tracked implement and viseversa. More particularly, this invention relates to how the mower andtracked implement convert using a common drive unit and to variousfeatures of the mower and tracked implement.

BACKGROUND OF THE INVENTION

In the field of outdoor power equipment, riding mowers are known forcutting large areas of grass. Such mowers typically comprise a framecarrying a prime mover and a cutting deck mounted to the frame. Theframe is supported for rolling over the ground by a pair of front casterwheels and a pair of rear drive wheels that are driven in some fashionfrom the prime mover. The drive wheels are often independently drivablein forward and reverse to provide zero radius turn (ZRT) capability. Anoperator is carried on a seat provided on the frame and operates thedrive wheels and steers the frame using various controls adjacent theseat.

As can be appreciated, the owner of such a mower has a substantialcapital investment in the mower. Yet, in northern climates, the mowermay not be used year round, but can sit idle during the winter. It wouldbe desirable if the mower could effectively do double duty and becustomarily used for winter snow removal operations. This would make thepurchase of such a mower more cost effective and easier to justify.

Attempts have been made in the past to adapt a mower for snow removal bymounting a snowblower or snowplow on the front of the mower. If thesnowblower is powered, a drive belt or other drive system would extendfrom the mower to the snowblower to power the snowblower. However, thebasic drive system of the mower is not changed. In other words, theweight distribution and traction characteristics that were designed intothe mower to give optimum performance as a mower are not changed merelyby adding a snowblower or snowplow to the front of the mower.

The traction characteristics of a riding mower might work adequately ona relatively dry surface and allow the mower to push a snowblower orsnowplow. But, these are not the surface conditions experienced whensnow removal is needed. The ground surface then is normally snowy and/oricy. Thus, the tractive ability of a mower, particularly of a largeriding mower carrying a seated operator, is not ideal or well suited foroperating on such a slick surface.

Using a normal riding mower for snow removal operations often results ina snow removal product that does not perform well and that tends to losetraction. As mentioned above, the mower's traction system is notdesigned for snowy conditions. Moreover, when a snowblower or rotarybrush or the like is added to the front of a mower, the added weight ofthis front mounted attachment tends to lift the drive wheels of themower off the ground, particularly when the attachment is lifted upabove the ground by some type of lift and lower system. In thissituation where the rear drive wheels are lifted upwardly relative tothe ground by the weight of the attachment, traction can be reduced somuch that climbing a curb or driving the mower onto a trailer becomesvery difficult or impossible.

Accordingly, dedicated, single purpose, tracked snow removal machineshave been developed for clearing snow. The owner can purchase suchmachines for use in snow removal operations during the winter. However,this does not solve the problem of cost effectiveness. The snow removalmachines sit idle during the summer, and the mower sits idle during thewinter. Essentially, the owner must purchase and maintain two sets ofequipment.

Thus, there is a need in the art for a product that would convertbetween a mower and a tracked implement and provide optimum traction andweight distribution in either form. This would be cost effective and yetgive good operational results whether mowing or using the trackedimplement for snow removal or some other non-grass mowing operation.

In using a machine of the type contemplated, whether in the mower ortracked implement form, it will often be necessary to climb smallobstructions such as a curb. The operator will often drive the machineup over a curb or off a curb as the machine is transported from one areato the next. This presents various problems to a tracked implement. Forexample, as a tracked implement climbs a curb, some of the track supportidlers or drive members will be up on top of the curb while others willstill be on level ground. This will stretch or elongate the track andquickly cause the track to fail.

Tracked implements often solve the problem of track elongation by usingidlers that are spring biased to accommodate the change in track length.However, this is a relatively complicated and costly track suspensionsystem that is difficult to maintain and keep clear in winteroperations. If a mower is to convert to a tracked implement, it would bedesirable to have a simple, durable and effective way of solving theproblem of track elongation.

Finally, in considering the operation of many known mowers of the typeunder consideration, the cutting deck is suspended from the frame of themower to follow the contours of the ground independently of the mower.This is best done with a relatively light cutting deck. However, lightcutting decks are not extremely durable and often wear quickly duringoperation.

One can attempt to improve the durability of a cutting deck byincreasing the weight of the deck using thicker and stronger materialsto form the deck. Such heavier decks, while more durable, tend toexhibit poorer ground following characteristics. For example, in thelowest or lower height of cut settings, such heavier decks will dig orplow into the ground despite using anti-scalp rollers, wheels or skidson the decks. This causes the cutting blades carried on the decks toscalp the turf. It would be desirable to have a relatively heavy cuttingdeck that still exhibits good ground following characteristics.

SUMMARY OF THE INVENTION

One aspect of this invention relates to a mower that converts into atracked implement. The invention comprises a drive unit which comprisesa drive frame, a prime mover carried on the drive frame, an operator'sstation on the drive frame for carrying an operator, a pair of groundengaging drive wheels on the drive frame with one drive wheel located oneach side of the drive frame for driven rotation about a commonrotational drive axis, and a control system on the drive frame adjacentthe operator's station for operating the drive wheels. A mower unit isprovided which comprises a mower frame, at least one ground engagingsupport wheel carried on the mower frame, and a grass cutting unitcarried on the mower frame. A tracked unit is provided which comprises atrack frame, a plurality of rotatable support idlers carried on thetrack frame with at least support one idler located on each side of thetrack frame, a device carried on the track frame to perform a ground orturf grooming or working operation other than grass cutting, and a pairof endless ground engaging tracks with one track located adjacent eachside of the track frame. Each track is entrained around and connects arotatable drive member carried on the drive frame and located on thedrive axis on one side of the drive frame to a support idler on acorresponding side of the track frame. Either the mower unit or thetracked unit are alternatively usable with the drive unit to provide,respectively, either a mower for cutting grass or a tracked implementfor performing the non-grass cutting ground or turf grooming or workingoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be described hereafter in the Detailed Description,taken in conjunction with the following drawings, in which likereference numerals refer to like elements or parts throughout.

FIG. 1 is a perspective view of a tracked implement according to thisinvention, particularly illustrating a tracked unit having beenreleasably joined to a separate, freestanding drive unit to form acomplete, operable tracked implement and illustrating a ground or turfgrooming or working device on the front of the tracked implement;

FIG. 2 is a side elevational view of the tracked implement of FIG. 1,but with the ground or turf grooming or working device not being shownon the front of the tracked implement;

FIG. 3 is a side elevational view similar to FIG. 2, particularlyillustrating the tracked implement in its separable parts comprising atracked unit and a drive unit prior to the tracked unit being joined tothe drive unit and prior to the installation of the endless groundengaging tracks, and further showing the cab on the tracked unit havingbeen pivoted forwardly to allow the rear of the cab to clear theoperator's seat when the tracked unit is being installed or removed fromthe drive unit.

FIG. 4 is an enlarged perspective view of a portion of the cab of thetracked implement of FIG. 1, particularly illustrating a manuallyoperable jack for pivoting the cab on the tracked unit relative to thetracked unit;

FIG. 5 is a side elevational view of a mower according to thisinvention, particularly illustrating the tracked unit having beenremoved from the drive unit and a mower unit in the process of beingjoined to the drive unit to convert the tracked implement of FIG. 1 to amower;

FIG. 6 is an enlarged perspective of a portion of the mower of FIG. 5,particularly illustrating the mower unit having been bolted to the driveunit to form a complete mower;

FIGS. 7-9 are diagrammatic side elevational views of the groundpropelling operation of the tracks of the tracked implement of FIG. 1,particularly illustrating the pivoting motion permitted for the frontand trailing idlers when the track climbs an obstruction such as a curb;

FIGS. 10-11 are diagrammatic side elevational views similar to FIGS.7-9, particularly illustrating that no pivoting motion is permitted forthe front and trailing idlers when the track drives off an obstructionsuch as a curb;

FIGS. 12-13 are diagrammatic side elevational views of the track removaloperation for the tracked implement of FIG. 1, particularly illustratinghow the front and trailing idlers can be released from the tracked unitto swing downwardly to release tension on the track;

FIG. 14 is a side elevational view of a portion of the tracked implementof FIG. 1, particularly illustrating one of the idler supports as wellas the pivotal hanger that connects the idler support to the track frameof the tracked unit, the pivotal hanger being shown secured to the trackframe in its normal operational position;

FIG. 15 is a side elevational view similar to FIG. 14, particularlyillustrating the pivotal hanger for the idler support having beenreleased from the track frame to permit the hanger and the idler supportto swing down relative to the tracked unit to the tension releasingposition that is diagrammatically illustrated in FIG. 13 for trackremoval and installation;

FIG. 16 is a side elevational view of a mower unit according to thisinvention, particularly illustrating the height of cut adjustment systemfor the cutting deck of the mower unit;

FIG. 17 is a top plan view of the mower unit of FIG. 16, particularlyillustrating the height of cut adjustment system and a hydrauliccylinder for lifting and lowering the cutting deck; and

FIG. 18 is a partial perspective view of a portion of the mower unit ofFIG. 16, particularly illustrating a weight transfer arm and a torsionspring for transferring some of the weight of the cutting deck to themower frame.

DETAILED DESCRIPTION

FIG. 1 illustrates one embodiment of a tracked implement 2 according tothis invention. Implement 2 preferably can be converted from a zeroradius turn (ZRT) mower 4 as shown in FIG. 5 and vice versa. In otherwords, as will be explained in more detail hereafter, mower 4 can bechanged into implement 2 and implement 2 can be changed back into mower4. This conversion is one aspect of this invention.

However, implement 2 and mower 4 need not necessarily be convertibleinto the other. Both implement 2 and mower 4 could be provided ascomplete machines that would not undergo any conversion. Other aspectsof this invention relate to how the endless tracks on implement 2 aresupported. Yet other aspects of this invention relate to how a cuttingdeck is suspended from mower 4. These other aspects of this inventionare not dependent upon being used only in a convertible implement 2 andmower 4.

The Drive Unit

There is a portion of both mower 4 and implement 2 that is common toeach. The common portion is a ZRT drive unit 6. Drive unit 6 is shown inFIG. 3 as part of what will become implement 2. The identical drive unit6 is shown in FIG. 5 as part of what will become mower 4.

Drive unit 6 includes a drive frame 8 which carries a prime mover 9,such as an internal combustion engine. Drive unit 6 also includes anoperator's station 10 provided on drive frame 8. Preferably, operator'sstation 10 includes a seat 12 for supporting a seated operator. However,operator's station 10 could comprise a platform for supporting astanding operator.

A pair of drive wheels 14 with rubber tires is provided on drive frame 8for self propelling drive unit 6 over the ground. There is a left drivewheel 14 and an identical right drive wheel (not shown). Preferably,drive wheels 14 operate in a ZRT fashion. Namely, each drive wheel 14 isdriven in forward and reverse independently of one another to allow bothpropulsion and steering of drive frame 8 using differential control ofdrive wheels 14. For example, to execute a zero radius turn or spinturn, one drive wheel 14 will be driven forwardly while the other drivewheel 14 is reversed.

Any suitable control system can be provided on drive frame 8 for use byan operator to control the operation of drive wheels 14. With ZRT drivewheels, one embodiment of a control system that may be used is a pair ofleft and right control sticks 16 that independently control theoperation of the left and right drive wheels. When each control stick 16is pushed forwardly by the operator out of a neutral position, thecorresponding drive wheel 14 is driven forwardly. When each controlstick 16 is pulled rearwardly by the operator out of a neutral position,the corresponding drive wheel 14 is driven rearwardly.

Thus, to execute a zero radius turn or spin turn, one control stick 16is pushed forwardly by the operator while the other control stick 16 issimultaneously pulled rearwardly by the operator. Both control sticks 16are arranged adjacent seat 12 for convenient access by the operator.Instead of twin control sticks 16, the control system could comprise arotatable steering wheel with a foot operated traction pedal forcontrolling the ground speed.

A traction system is provided on drive frame 8 for independentlypowering drive wheels 14 in the aforementioned manner. One commontraction system comprises a pair of left and right hydraulic motors (notshown) whose drive shafts are coupled to the left and right drive wheels14, respectively. One or more hydraulic pump (not shown) and hydraulicreservoir (not shown) are carried on drive frame 8 and the pump isdriven by prime mover 9 to supply pressurized hydraulic fluid to thehydraulic motors. Thus, drive wheels 14 are driven by prime mover 9through the hydraulic pump and the hydraulic motors. Non-hydraulictraction systems could be used in place of a hydraulic drive system toindependently rotate drive wheels 14.

It is preferred that drive wheels 14 of drive unit 6 be capable of ZRToperation as described above. However, drive wheels 14 could be drivenin a non ZRT mode. For example, drive wheels 14 could be mounted on theend of a conventional transaxle having a differential. In this case,drive wheels 14 rotate in forward and reverse simultaneously with thedifferential allowing drive wheels 14 to rotate at different speedsduring a turn. Unlike the ZRT drive wheels in which one wheel can rotateforwardly while the other rotates rearwardly, a drive unit equipped witha transaxle/differential drive does not permit drive wheels 14 to rotatein different directions simultaneously. Thus, with this latter type ofdrive, the turning radius of drive unit 6 will be increased.

A pair of left and right mounting posts 18 are provided on drive frame 8behind and below the top of operator's seat 12. Only the right mountingpost 18 is shown in FIG. 3. The left mounting post is identical but ishidden in FIG. 3. As will be described in more detail hereafter,mounting posts 18 will serve as attachment points for differentcomponents when drive unit 6 is used as part of implement 2 or mower 4,as shown in FIGS. 3 and 5.

Drive unit 6 includes a forwardly extending power takeoff shaft (PTO) 20for providing mechanical power from prime mover 9 to various componentson implement 2 or mower 4. See FIG. 5. In addition, when drive unit 6includes one or more hydraulic pumps and reservoir, drive unit 6includes a pair of hydraulic output and return-hoses 22. See FIG. 3.Hydraulic hoses 22 serve to supply hydraulic power to implement 2 ormower 4. Pressurized fluid flows from the pump through output hose 22_(o) and returns to the reservoir through the return hose 22 _(r).Obviously, hoses 22 will be connected to similar hoses provided onimplement 2 or mower 4 when implement 2 or mower 4 also includes ahydraulically powered component. The connection between hoses 22 ondrive unit 6 and the hoses on implement 2 or mower 4 will be made usingconventional quick connectors.

Obviously, drive unit 6 as disclosed herein is not a complete, operativeimplement 2 or mower 4 by itself. For one thing, it is supported formovement only by a single pair of drive wheels 14 so that it would notbe stably supported for movement over the ground even if the weight ofdrive unit 6 were balanced over drive wheels 14. Drive unit 6 will tiltone way or the other unless supported by jacks or jack stands. Whenoperator's station 10 includes an operator's seat 12, there is nofloorboard or footrests on drive unit 6 on which the operator's feet canrest. Instead, the operator's lower legs and feet would dangle in freespace ahead of drive unit 6. Finally, there is no working device carriedon drive unit 6 for providing any type of ground or turf grooming orworking operation.

Thus, it is self-evident that something must be coupled to drive unit 6to make it into implement 2 or mower 4. In the case of mower 4, a mowerunit is coupled to drive unit 6 using a first set of mounting holes 24provided on each side of drive frame 8. In the case of implement 2, atracked unit 28 is coupled to drive unit 6 using a second lower andrearward set of mounting holes 26 provided on drive frame 8. While it iseasier to use different sets of mounting holes 24 or 26 to attach eitherthe mower unit or tracked unit 28 to drive unit 6 given their differentgeometries, it would be possible to design the mower unit and trackedunit 28 to use the same set of mounting holes on drive frame 8. In thiscase, only a single set of mounting holes would be provided on eitherside of drive frame 8.

The description of this invention will continue with separatedescriptions of tracked unit 28 and the mower unit.

The Tracked Unit

Tracked unit 28 comprises a track frame 30 having a set of attachmentholes 32 on either side of track frame 30 that match the lower rearwardset 26 of the mounting holes on drive frame 8. Track frame 30 can berolled back towards drive frame 8 as indicated by the arrow A in FIG. 3.When the two approach each other, attachment holes 32 on each side oftrack frame 30 can be aligned with mounting holes 26. A plurality ofbolts can then be installed through the aligned attachment and mountingholes to rigidly join track frame 30 of tracked unit 28 to drive frame 8of drive unit 6.

Track frame 30 includes a floorboard 34 and footrests 36 for supportingthe feet of the operator when tracked unit 28 is coupled to drive unit6. When the two are secured together, floorboard 34 and footrests 36will be immediately in front of and below seat 12 in operator's station10. Thus, as the operator sits on seat 12, the operator's lower legs andfeet will be comfortably supported on floorboard 34 and/or footrests 36provided on tracked unit 28. This is one way that tracked unit 28completes or finishes drive unit 6 to form a complete, operativeimplement.

Track frame 30 of tracked unit 28 carries a cab 38 for enclosingoperator's station 10 when tracked unit 28 is married with drive unit 6.Cab 38 has a framework 40 that supports a plurality of glass panels 42to allow the operator good visibility out of cab 38. The shape of cab 38and the number and placement of glass panels 42 can obviously vary. Cab38 is topped by a roof 43 and includes a door 41 that can be opened andclosed.

The overall purpose of cab 38 is to substantially completely surroundthe operator and protect the operator from the elements as the operatoris supported at operator's station 10. Cab 38 is particularly importanton tracked unit 28 since many of the ground or turf grooming or workingdevices used in conjunction with tracked unit 28 will be used during thewinter when the weather is cold.

The front of cab 38 is pivotally mounted to track frame 30 by a pair ofcompressible rubber mounts 44. One such rubber mount 44 is shown in FIG.4. If the rear of cab 38 is pushed upwardly, cab 38 will pivot or rockforwardly on rubber mounts 44. This forward rocking of cab 38 isillustrated in FIG. 3. Rubber mounts 44 will compress as need be toallow this pivoting or rocking motion of cab 38.

In fact, cab 38 will need to be rocked forwardly on rubber mounts 44during the process of coupling or uncoupling tracked unit 28 from driveunit 6. The rear of cab 38 has a pair of left and right mounts 46 thatbolt to mounting posts 18 that are located on drive frame 8 behind andbelow seat 12. Securing cab 38 to drive frame 8 behind and below seat 12is preferred so that the rear of cab 38 snugs up to drive frame 8without leaving any large openings behind seat 12. Accordingly, it isnecessary to rock cab 38 forwardly to allow mounts 46 on cab 38 to clearseat 12 when tracked unit 28 is being rolled towards or away from driveunit 6. When tracked unit 28 is being joined to drive unit 6, theforward rocking of cab 38 can be discontinued after mounts 46 pass overseat 12 and cab 38 will settle back down into a non-rocked, normaloperational posture with mounts 46 on the rear of cab 38 mating withposts 18 on drive frame 8.

FIG. 4 discloses a simple jack 48 that can be selectively used to rockcab 38 forwardly about rubber mounts 44. Jack 48 is an elongated bar 50that is long enough to span the width of cab 38. Bar 50 also engagestowards the rear of cab 38 against the underside of some of thelongitudinal frame members of cab framework 40. Bar 50 includes athreaded nut 52 fixed to the bottom of each side of bar 50. A pair ofthreaded bolts 54 extend downwardly through bar 50 and are threaded intoand through nuts 50. The top hex head of each adjusting bolt 54 islocated above bar 50 and the lower end of bolt 54 is below bar 50.

When jack 48 is positioned as shown in FIG. 4, the operator can rock cab38 forwardly about its rubber mounts 44 by raising bar 50 upwardly usingthreaded adjusting bolts 54. When the lower ends of bolts 54 are engagedagainst track frame 30 of tracked unit 28 as shown in FIG. 4, rotatingbolts 54 in the correct direction will cause bar 50 to rise upwardly dueto threaded nuts 52 carried on bar 50. If bar 50 is raised far enough asshown in FIG. 3, cab 38 will then be sufficiently rocked forwardly onrubber mounts 44 to allow mounts 46 on cab 38 to clear seat 12.

Jack 48 can be left in place in tracked unit 28 in this raised positionwhenever tracked unit 28 is not joined to drive unit 6. For example, iftracked unit 28 has been removed from drive unit 6 for storage duringthe offseason, jack 48 will normally simply be left in place. However,jack 48 can be easily removed if desired and would be removed whentracked unit 28 is joined to drive unit 6. Jack 48 can be removed bylowering bar 50 on bolts 54 until bar 50 disengages framework 40 of cab38 after cab 38 has leveled out. Jack 48 can then be lifted out of cab38 by opening door 41 of cab 38 and lifting jack 48 out through the opendoor 41 of cab 38.

Each side of track frame 30 includes a pair of idlers 56 that willsubsequently partially support an endless ground engaging belt or track58. Idlers 56 preferably comprise a pair of support wheels with rubbertires. This allows tracked unit 28 to roll over the ground when theendless tracks 58 are not yet installed. This is the situation prior totracked unit 28 being joined to drive unit 6 as shown in FIG. 3. Thesupport wheels comprising idlers 56 clearly permit rolling movement oftracked unit 28 towards and away from drive unit 6.

Each pair of idlers 56 on each side of track frame 30 comprises a frontidler 56 _(f) and a trailing idler 56 _(t) located behind front idler 56_(f). These two idlers are supported on track frame 30 in a novel mannerproviding various advantages.

First, front idler 56 _(f) and trailing idler 56 _(t) on each side oftrack frame 30 are both rotatably journalled on a common idler support60 about axes of rotation that are fixed relative to idler support 60.Front idler 56 _(f) rotates on the front of idler support 60 about afront idler axis 62. Trailing idler 56 _(t) rotates on the rear of idlersupport 60 about a trailing idler axis 64. Idler support 60 is itselfpivotal relative to track frame 30 about an idler support pivot axis 66.Idler support pivot axis 66 is located between front idler axis 62 andtrailing idler axis 64.

In fact, the location of idler support pivot axis 66 is carefully chosento prevent track elongation when tracked unit 28 climbs an obstruction,such as a curb or the like. The Applicants have found that placing idlersupport pivot axis 66 to the rear of the midpoint between front idleraxis 62 and trailing idler axis 64, i.e. closer to trailing idler axis64 than to front idler axis 62, is desirable. When the rearward locationof idler support pivot axis 66 is properly chosen, the overall geometryis effective to keep the overall track length substantially constantwhen implement 2 climbs up over an obstruction through an angle ofinclination of at least approximately 15° or less.

The exact rearward location of idler support pivot axis 66 can be foundthrough trial and error or by calculation. One simply incrementallymoves the location of idler support pivot axis 66 and then measures orcalculates the amount of track elongation at various angles ofinclination. The location that provides the least track elongation, andpreferably substantially no track elongation, through the desirablerange of angles, from 0° through approximately 15°, is then chosen.

FIGS. 7-9 illustrate what happens when implement 2 climbs up over anobstruction that produces an angle of inclination of track 58 within theselected range. As front idler 56 _(f) reaches the obstruction and risesup onto the obstruction, trailing idler 56 _(t) will remain on levelground. Idler support 60 that couples front idler 56 _(f) and trailingidler 56 _(t) will pivot on track frame 30 to accommodate this situationwith front idler 56 _(f) rising upwardly and trailing idler 56 _(t)falling downwardly relative to their previous positions. Compare FIG. 8to FIG. 7 to see the relative positions of idlers 56 produced by thepivotal motion of idler support 60. Of course, as shown in FIG. 9, oncetracked unit 28 has climbed up the obstruction and reaches level ground,the positions of the front and trailing idlers revert to their usualnormal operational positions in which front idler axis 62, idler supportpivot axis 66, and trailing idler axis 64 are all in line and aresubstantially horizontal.

As described previously, when the location of idler support pivot axis66 is properly chosen, there will be no substantial amount of trackelongation when climbing obstructions within the selected range ofinclination. This means that the front and trailing idlers 56 can bemounted to idler support 60 on fixed pivot axes and do not need to slidetowards and away from one another as would be typical for trackedvehicles. Thus, the relatively rigid and pivotal suspension system foridlers 56 is extremely simple, durable and cost effective and avoids theneed for a spring biased suspension on idlers 56. Yet, implement 2 canstill climb obstructions without elongating track 58 to provide adequatetrack tension.

Referring now to FIGS. 10 and 11, when implement 2 drives off a similarobstruction, pivoting of idler support 60 in the opposite direction isprevented or stopped. Thus, referring to FIG. 10, as front idler 56 _(f)passes off the obstruction and with trailing idler 56 _(t) still on theobstruction, allowing front idler 56 _(f) to pivot down would causeunacceptable track elongation. Thus, this movement of front idler 56_(f) is positively prevented. After both the front and trailing idlers56 have dropped off the obstruction, idler support 60 can still pivot inthe manner noted above to accommodate the position of the rear tracksupport in the form of drive wheel 14 when drive wheel 14 is still ontop of the obstruction. See FIG. 11.

Idler support 60 on each side of track frame 30 is itself carried on oneend of a pivotal arm or hanger 68. Idler support pivot axis 66 iscarried on hanger 68 so that hanger 68 connects to idler support 60between front idler axis 62 and trailing idler axis 64 as shown in FIGS.14 and 15. During normal operation of implement 2, hanger 68 is fixed totrack frame 30 by an attachment bolt 70 carried on hanger 68. Bolt 70may be secured by a nut 72 to a flange 74 on track frame 30. The fixedlocation of hanger 68 is shown in FIG. 14 with the usual pivotal motionof idler support 60 that was previously discussed in conjunction withFIGS. 7-9 being shown in phantom lines in FIG. 14.

Hanger 68 is pivoted to track frame 30 at its other end, namely at theend of hanger 68 that does not hold idler support 60. Thus, hanger 68 ispivotal relative to track frame 30 about a hanger pivot axis 76 shown inFIGS. 14 and 15. If track frame 30 is jacked up above the ground and ifnut 72 is removed from bolt 70, hanger 68 will be released from trackframe 30 to pivot downwardly. Hanger 68 is shown in its downwardlypivoted position in FIG. 15. Hanger 68 is selectively put into thisposition in order to install or remove track 58 from front idler 56_(f), trailing idler 56 _(t) and drive wheel 14.

FIGS. 12 and 13 help illustrate what happens when hanger 68 isdisconnected from track frame 30. FIG. 12 shows the situation whenhanger 68 is still rigidly attached to track frame 30 by bolt 70. Inthis position, corresponding to normal operations of implement 2, frontidler 56 _(f), trailing idler 56 _(t) and drive wheel 14 are all in linewith track 58 being entrained around them and being properly tensioned.However, if bolt 70 is disconnected from track frame 30, then hanger 68pivots downwardly to the position shown in FIG. 13. In this position,trailing idler 56 _(t) has swung back to abut against drive wheel 14 andfront idler 56 _(f) has pivoted downwardly by a fair amount. There isnow considerable slack in track 58.

To remove track 58 with the parts as shown in FIG. 13, one could simplyslide track 58 off to one side of front idler 56 _(f), trailing idler 56_(t), and drive wheel 14. However, if this cannot easily be done by theoperator, then trailing idler 56 _(t) and/or drive wheel 14 could alsobe removed from idler support 60 leaving track 58 entrained around onlyfront idler 56 _(f) or around front idler 56 _(f) and drive wheel 14.The jack holding track frame 30 upwardly can then be lowered enough toallow hanger 68 to be resecured to track frame 30. Traction frame 30 canthen be jacked back up to allow track 58 to be easily slid off to oneside of front idler 56 _(f) or front idler 56 _(f) and drive wheel 14.This process is repeated on both sides of track frame 30.

With both tracks 58 removed, each trailing idler 56 _(t) can beremounted to each idler support 60 if it was removed during the trackremoval process. In addition, drive wheels 14 used for mower 4 areinstalled back on drive unit 6. If the jack holding track frame 30 offthe ground during this track removal process is now released andremoved, track frame 30 will settle back down onto the ground, nowsupported by front idler 56 _(f) and trailing idler 56 _(t), both ofwhich are rubber tired wheels.

With track frame 30 unbolted from drive frame 8 of drive unit 6, trackedunit 28 can now simply be rolled away from drive unit 6 for storage.This assumes, of course, that cab 38 has also been disconnected fromdrive frame 8 and has been rocked forwardly to allow cab 38 to clearseat 12. This also assumes that any connections between PTO 20 and thehydraulic hoses 22 on drive frame 8 and any mechanically orhydraulically powered equipment on track frame 30 have been released atsome point in this process. Electrical and heater hoses (not shown) forcab 38 will also need to be disconnected. Nonetheless, it is quitesimple and fairly easy to install and remove tracked unit 28 from driveunit 6 when forming or disassembling tracked implement 2 of thisinvention. This can also be done relatively quickly.

The stop 78 that limits or prevents pivotal motion of idler support 60in one direction can be seen in FIGS. 14 and 15 on the underside ofhanger 68. This stop 78 abuts against the top of idler support 60rearwardly of idler support pivot axis 66 to prevent what would becounter-clockwise rotation of idler support 60 in FIG. 14. Onlyclockwise rotation of idler support 60 is permitted. This permittedrotation is that in which the rear of idler support 60 pivots or movesdownwardly away from stop 78.

Preferably, stop 78 is adjustable downwardly from the position shown inFIGS. 14 and 15 if desired to adjust how track 58 lies against theground in the normal, operational position of track 58. If conditionsare icy and snowy and one wishes maximum traction, then the orientationshown in FIGS. 14 and 15 would be used. In this orientation asdiagrammatically shown in FIG. 12, track 58 lies flat against the groundover its entire length.

However, with this substantially flat track orientation, tracks 58 willscrub when turning. If conditions are relatively dry such as when thereis no snow or ice on the ground, or when operating on a dry smoothsurface such as a paved road, it might be desirable to move stops 78 oneach idler support 60 downwardly to force trailing idler 56 _(t)downwardly relative to front idler 56 _(f) and drive wheel 14. Stops 78can be adjusted downwardly by shimming them downwardly or by using someother adjustment mechanism such as a threaded adjustment rod. This willcreate more of a point contact between track 58 and the ground as track58 now forms a slight V-shape relative to the ground about trailingidler 56 _(t). This reduces the scrubbing effect when turning.Obviously, this adjustment of stop 78 is done selectively to account forsurface conditions and will be left unchanged until the operator wishesto make a change.

Finally, implement 2 will carry some kind of a device 80 on the frontthereof for performing some type of ground or turf grooming or workingoperation other than grass cutting. The front of track frame 30 includesan A-frame quick attachment 82 for holding a variety of devices 80. Forexample, a portion of a housing of a rotary brush 84 is shown in FIG. 1which brush rotates around a transverse, horizontal axis for brushingsnow off a sidewalk or road. A powered two stage snowthrower couldcomprise device 80. Other powered or even non-powered devices 80, suchas a snowplow blade, could be carried on quick attachment 82. Thus,device 80 attached to implement 2 could have a variety of forms.

Typically, A-frame quick attachment 82 will have a hydraulic lift andlower system represented by hydraulic connections 86 for allowingattachment 82 to be raised or lowered to raise and lower device 80connected to quick attachment 82. This lift and lower system is whatwill be connected to the hydraulic output and return hoses 22 on driveunit 6. This provides the operator with selective control of thevertical position of device 80 from seat 12 on drive unit 6. Inaddition, tracked unit 2 will typically include another hydraulic systemfor providing left and right pivoting of device 80 or some portion ofdevice 80 relative to a fore-and-aft axis, such as adjusting the angleof a straight plow blade, or the angle of a snow discharge chute on atwo stage snowthrower, or the angle of a rotary brush 84.

In addition, many devices 80, such as the aforementioned rotary brush 84or two stage snowthrower, will be mechanically powered. When amechanically powered device 80 is used on quick attachment 82, such adevice 80 will be driven using PTO 20 on drive unit 6. Obviously, ifdevice 80 is powered in some other way or is unpowered, such as a staticsnowplow blade, then PTO 20 on drive unit 6 would not be utilized bytracked unit 28.

The Mower Unit

FIGS. 5 and 6 show a mower unit 88 that can be used with drive unit 6 inplace of tracked unit 28 to convert tracked unit 28 into mower 4. Mowerunit 88 as shown in FIGS. 5 and 6 comprises a generally U-shaped mowerframe 90 having a pair of rearwardly extending arms 92 each having a setof attachment holes 94 therein. Attachment holes 94 match the pattern ofthe mounting holes provided in the upper set 24 of mounting holes oneach side of drive unit 6. Thus, mower frame 90 may be bolted to driveframe 8 after attachment holes 94 and mounting holes 24 are aligned withone another and a plurality of bolts 96 are inserted through the alignedholes. This attachment between mower frame 90 and drive frame 8 is shownin FIG. 6 along one side of mower frame 90 and drive frame 8.

Mower frame 90 is supported by a pair of front support wheels 98attached adjacent the front corners of mower frame 90. Support wheels 98are non-driven caster wheels. Like track frame 30, mower frame 90provides a floorboard 99 and footrests 100 for the operator's feet whenmower unit 88 is joined to drive unit 6. Drive unit 6 still has a pairof drive wheels 14 thereon which along with support wheels 98 on mowerframe 90 support mower 4 for rolling over the ground. However, whendrive unit 6 is mated with mower unit 88 to form a complete, operativemower 4, drive wheels 14 have a larger diameter than the drive wheels 14that are used on drive unit 6 when drive unit 6 is mated with trackedunit 28.

Mower frame 90 carries a generally conventional cutting unit 102.Cutting unit 102 preferably comprises a rotary cutting deck 104 thatforms a downwardly facing cutting chamber or chambers in which one ormore rotary cutting blades (not shown) are carried. The cutting bladesrotate about generally vertical axes in horizontal cutting planes. Theperipheral skirt of the cutting deck is provided with various anti-scalpground engaging wheels, rollers and/or skids 106. Other cutting units102 besides rotary cutting decks 104 could be employed on mower frame90.

Cutting deck 104 is suspended from mower frame 90 by a plurality ofsuspension chains 108 that extend between cutting deck 104 and the lowerends of a plurality of L-shaped height of cut adjustment links 110. Fourchains 108 and four links 110 are provided spaced apart in a rectangularpattern. Each link 110 is pivotally carried on mower frame 90 by virtueof being mounted on a pivot axis 112. The height of cut provided bycutting deck 104 can be varied by simultaneously pivoting all four links110 to raise or lower the upper suspension points of the fixed lengthchains 108, thus raising or lowering cutting deck 104 relative to theground. The use of chains 108 connected between a cutting deck 104 and aplurality of pivotal links 110 is a well known height of cut adjustmentsystem in the mower art.

Referring to FIG. 17, the links 110 are all connected together so thatpivoting one link 110 will pivot the rest of links 110. A hydrauliccylinder 114 is connected by a bracket 116 to pivot the right rear link110 (shown in the upper left in FIG. 17). The right rear link 110 isconnected to the left rear link 110 by a cross-shaft 117. Each of therear links 110 are secured by connecting rods 118 to the front links110. Thus, rotation of the right rear link 110 will rotate all of theother links 110 in the same direction of rotation about their pivot axes112. Links 110 could be rotated without using hydraulic cylinder 110using a hand lever, a foot pedal, both a hand lever and foot pedal, etc.

Referring to FIG. 16, cylinder 114 is also operatively connected to aheight adjustment stop 120 for rotating stop 120 as cylinder 114 isextended and retracted. Stop 120 is placed adjacent to an arcuatelocking plate 122 having an arcuate array of height adjustment holes124. A limit pin 126 is inserted through a selected hole in the array ofheight adjustment holes 124 so as to be in position to abut against therear of stop 120 at some point in the rotational motion of stop 120. Thelocation of limit pin 126 establishes the height of cut.

Referring to FIG. 16, if cylinder 114 is extended, this will pivot allthe links 110 in a counter-clockwise direction indicated by the arrowCCW in FIG. 16. This moves stop 120 away from limit pin 126. Thus,cylinder 114 can extend to its full stroke to lift cutting deck 104 to amaximum upper transport position. In this transport position, cuttingdeck 104 is spaced well above the ground and mower 4 can be transportedat a higher speed than the speed normally used to cut grass.

Cylinder 114 is allowed to retract simply by permitting hydraulic fluidto flow back to the reservoir through hydraulic return hose 22 _(r) byopening a valve (not shown) in the hydraulic circuit to cylinder 114.The weight of cutting deck 104 then forces cylinder 114 to retract.

When cylinder 114 retracts, links 110 will rotate in a clockwisedirection indicated by the arrow CW in FIG. 16. This moves stop 120 backtowards limit pin 126 and simultaneously begins to lower cutting deck104 downwardly from its transport position. When stop 120 engagesagainst limit pin 126, further retraction of cylinder 114 is preventedand the downward lowering movement of cutting deck 104 stops. Thelocation of limit pin 126 within the arcuate array of holes 124determines when this occurs to set the cutting height. The cuttingheight is lower the further limit pin 126 is set to the rear of thearcuate array of adjustment holes 124.

In this height adjustment system, cylinder 114 forms both lifts cuttingdeck 104 into an elevated position and holds cutting deck 104 in thatposition until the hydraulic fluid in cylinder 114 is permitted toreturn to the reservoir. Cylinder 114 also functions as part of theheight of cut adjustment system. The extension and retraction ofcylinder 114 is what causes the height adjustment stop 120 to move awayfrom or approach limit pin 126. The adjustment holes 124 in the arcuatearray of holes can be provided in a plurality of vertical rows as shownin FIG. 16 with the holes 124 in each row being slightly offset relativeto the holes in the other rows. This provides incremental heightadjustment settings between the settings that would otherwise beobtainable if only one arcuate row of holes 124 is used. Thus, a veryefficient and cost effective height of cut adjustment system isdisclosed.

Cylinder 114 obviously is powered by hydraulic fluid. As noted earlier,this fluid is supplied to cylinder 114 by the hydraulic output hose 220on drive unit 6. The fluid returns from cylinder 114 to the reservoir ofthe hydraulic system through the hydraulic return hose 22 _(r) on driveunit 6. Thus, the hydraulic output and return hoses 22 on drive unit 6are obviously connected or coupled in some manner to cylinder 114.Similarly, PTO 20 on drive unit 6 is connected to a gearbox 128 thatprovides a mechanical drive to the rotary cutting blades in cutting deck104. See FIG. 17. The blades on cutting deck 104 could be hydraulicallypowered instead of being mechanically powered, in which case gearbox 128and a connection to PTO 20 would not be used.

Preferably, cutting deck 104 is manufactured of heavy, durable 7 gaugesteel. Thus, cutting deck 104 will typically weigh approximately 400 to500 lbs. When going over a rise or bump in the ground, there are severalanti-scalp rollers, wheels and/or skids 106 on cutting deck 104 to helpguide cutting deck 104 over the bump. But, with such a heavy cuttingdeck, the anti-scalp members 106 on the sides of cutting deck 104 willoften plow through or dig into the ground allowing the cutting blades toscalp. Also, anti-scalp members 106 can plow sideways into the turfduring a turn leaving a furrow. This is obviously undesirable.

In mower unit 88 of this invention, there are a pair of weight transferarms 130 that extend between the top of cutting deck 104 and mower frame90. One arm 130 is used on each side of cutting deck 104 at the front ofmower frame 90. FIGS. 16 and 18 show one such arm 130, the other arm 130being substantially identical. Arms 130 also provide fore-and-aftlongitudinal and left and right transverse horizontal stability tocutting deck 104.

Referring to FIGS. 16 and 18, each arm 130 is pivoted at its upper endat 132 to a flange 134 on the underside of mower frame 90. The lower endof arm 130 is pivoted on a horizontal pivot shaft 136 carried on the topof cutting deck 104. Pivot shaft 136 is supported on a bracket 138 oncutting deck 104 and is arranged quite close to one of the suspensionchains 108. Pivot shaft 136 extends all the way through the lower end ofarm 130 to be supported on the far side in FIG. 18 by another bracket138.

The lower end of arm 130 has a cutout or recess 140 in which a torsionspring 142 is received. Spring 142 concentrically surrounds pivot shaft136 on which the lower end of arm 130 pivots. One end of spring 142 isanchored to the top of cutting deck 104. The other end of spring 142abuts against the underside of a lip 144 on arm 130 or is connected toarm 130 in some other manner. The force of spring 142 will tend to pushupwardly on lip 144 to rotate arm 130 in the direction indicated by thearrow B in FIG. 18. This is the direction in which the lower end of arm130 tends to rise or lift to help transfer some of the weight of cuttingdeck 104 to mower frame 90.

As the height of cut of cutting deck 104 is lowered by the height of cutadjustment system, lip 144 on arm 130 will tend to further wind upspring 142. Thus, at the lowest height of cut of cutting deck 104,spring 142 will provide a maximum amount of upward bias. Preferably, thepair of springs 142 will transfer at least approximately 100 pounds ofthe 400 to 500 pounds of weight in cutting deck 104 to mower frame 90.This will make the anti-scalp members 106 on cutting deck 104 moreeffective in preventing scalping.

While two weight transfer arms 130 and two torsion springs 142 have beenshown herein for use with cutting deck 104, the number of such arms 130and springs 142 can vary. For example, four such arms 130 and four suchsprings 142 could be used. In this latter event, each arm 130 willconnect to cutting deck 104 generally adjacent the spot where eachsuspension chain 108 connects to cutting deck 104.

A roll over protection system (ROPS) 146 on mower 4 comprises a U-shapedroll over bar. The ends of the bar are bolted to the same mounting posts18 on drive frame 8 to which the mounts 46 on cab 38 had previously beenbolted when tracked unit 28 was joined to drive unit 6. ROPS 146 helpsprotect the operator in the event mower 4 is operated inappropriately insuch a way that mower 4 rolls over.

Conversion Between the Tracked Implement and the Mower

When drive unit 6 is mated with mower unit 88, the two together form acomplete and operative mower 4 having a rotary cutting deck 104.However, as is clear from the above, it is relatively easy to convertmower 4 into a tracked implement 2. This is done by unbolting mowerframe 90 from drive frame 8 and by disconnecting all other connections,such as the PTO 20 and the hydraulic hoses 22. Once so disconnected,mower unit 88 can simply be rolled away and stored as support wheels 98carried on mower frame 90 allow for rolling of mower unit 88. Inaddition, ROPS 146 will be disconnected from mounting posts 18. A toolcan be used with the rear of cutting deck 104 or mower frame 90 to helpsupport mower unit 88 while it is being disconnected and as it is beingstored during the winter.

After mower 4 is disassembled, tracked unit 28 can be rolled towardsdrive unit 6 using the support wheels that comprise front idler 56 _(f)and trailing idler 56 _(t). This is done as previously described abovein the description of tracked unit 28. During this process, drive wheels14 on drive unit 6 will be changed to smaller diameter drive wheelsmatching the diameter of front idler 56 _(f) and trailing idler 56 _(t),traction frame 30 and cab 38 will be bolted to drive frame 8, and tracks58 will be entrained around front idler 56 _(f), trailing idler 56 _(t)and drive wheels 14. The conversion to tracked implement 2 is nowcomplete save for the task of connecting PTO 20 and hydraulic hoses 22to whatever mechanically or hydraulically powered equipment is presentor carried on track frame 30 and for connecting the electrical andheater hoses for cab 38.

This invention provides for both a mower 4 and a tracked implement 2that convert from one to the other using a single common drive unit 6.Thus, this invention provides effective cost management for users ofsuch equipment as it will be less expensive to purchase the threecomponents of this invention, namely drive unit 6, mower unit 88 andtracked unit 28, than purchasing two complete, stand alone, singlepurpose machines. Moreover, implement 2 provided by this invention isone that is a true tracked unit and is not simply a mower that issomehow fitted out with a different grooming or working device. Inimplement 2 of this invention, the track geometry, weight distribution,etc., are all design to give optimum performance as a tracked implement.

Yet, despite the obvious cost savings, the conversion between mower 4and implement 2 can be quickly done. The number and types of stepsrequired to effect this conversion have been kept to a minimum. Cab 38is part of implement 2 and only needs to be bolted at the rear of cab 38to drive frame 8 of drive unit 6. Front idler 56 _(f) and trailing idler56 _(t) are released to move to their track removal and installationposition by releasing only a single nut 72 from a bolt 70. The totaltime required to make a complete conversion will be only a couple ofhours or so.

Various modifications of this invention will be apparent to thoseskilled in the art. While tracks 58 are preferably entrained aroundrotatable rubber tired wheels 14, 56 _(f) and 56 _(t), such wheels couldbe replaced by toothed sprockets when converting mower 4 to trackedimplement 2. However, one advantage of using wheels instead of sprocketsis that tracked unit 28 can simply be rolled away for storage oncetracks 58 are removed.

Thus, this invention is to be limited only by the appended claims.

1. A mower that converts into a tracked implement, which comprises: (a)a drive unit, which comprises: (i) a drive frame; (ii) a prime movercarried on the drive frame; (iii) an operator's station on the driveframe for carrying an operator; (iv) a pair of ground engaging drivewheels on the drive frame with one drive wheel located on each side ofthe drive frame for driven rotation about a common rotational driveaxis; and (v) a control system on the drive frame adjacent theoperator's station for operating the drive wheels; (b) a mower unit,which comprises: (i) a mower frame; (ii) at least one ground engagingsupport wheel carried on the mower frame; and (iii) a grass cutting unitcarried on the mower frame; (c) a tracked unit, which comprises: (i) atrack frame; (ii) a plurality of rotatable support idlers carried on thetrack frame with at least one support idler located on each side of thetrack frame; (iii) a device carried on the track frame to perform aground or turf grooming or working operation other than grass cutting;and (iv) a pair of endless ground engaging tracks with one track locatedadjacent each side of the track frame, wherein each track is entrainedaround and connects a rotatable drive member carried on the drive frameand located on the drive axis on one side of the drive frame to asupport idler on a corresponding side of the track frame; and (d)wherein either the mower unit or the tracked unit are alternativelyusable with the drive unit to provide, respectively, either a mower forcutting grass or a tracked implement for performing the non-grasscutting ground or turf grooming or working operation.
 2. The mower ofclaim 1, wherein the rotatable drive members carried on the drive framewhen the tracked unit is used with the drive unit are different from thedrive wheels carried on the drive frame when the mower unit is used withthe drive unit.
 3. The mower of claim 1, wherein the rotatable drivemembers carried on the drive frame when the tracked unit is used withthe drive unit are drive wheels having a smaller diameter than the drivewheels carried on the drive frame when the mower unit is used with thedrive unit.
 4. The mower of claim 3, wherein the rotatable supportidlers carried on the track frame are support wheels having the smallerdiameter of the drive wheels carried on the drive frame when the trackedunit is used with the drive unit.
 5. The mower of claim 1, wherein theground or turf grooming or working operation performed by the device onthe tracked unit is chosen from a group of operations comprisingsnowblowing, surface brushing, and plowing.
 6. The mower of claim 1,wherein the grass cutting unit comprises at least one rotatable cuttingblade that is rotatable about a substantially vertical axis in ahorizontal cutting plane.
 7. The mower of claim 6, wherein the cuttingblade(s) are located beneath a cutting deck carried on the mower frame.8. The mower of claim 7, wherein the cutting deck comprises a groundfollowing cutting deck that is movable relative to the mower frame inresponse to changes in ground contour.
 9. The mower of claim 7, whereinthe cutting deck is suspended from the mower frame by a plurality offlexible members.
 10. The mower of claim 9, wherein the flexible membersextend from the cutting deck to a plurality of pivotal height of cutadjustment links carried on the mower frame.
 11. The mower of claim 1,wherein the drive frame includes a power takeoff shaft for providingmechanical power from the prime mover to the grass cutting unit of themower unit or to the device of the tracked unit depending upon whetherthe mower unit or the tracked unit is used with the drive unit.
 12. Themower of claim 11, wherein the drive frame includes a pair of hydraulichoses carried on the drive frame for supplying pressurized hydraulicfluid to the mower unit or to the tracked unit depending upon whetherthe mower unit or the tracked unit is used with the drive unit and forreturning the pressurized hydraulic fluid to the drive unit.
 13. Themower of claim 1, wherein the operator's station includes a seat for aseated operator.
 14. The mower of claim 13, further including afloorboard for supporting the operator's feet when the operator isseated on the seat.
 15. The mower of claim 14, wherein the floorboard ispart of the mower frame or the track frame depending upon whether themower unit or the tracked unit is used with the drive unit.
 16. Themower of claim 14, further including a cab for substantially enclosingthe operator's station and the floorboard on the track frame when thetracked unit is used with the drive unit.
 17. The mower of claim 16,wherein the cab is carried on the track frame.
 18. The mower of claim17, wherein the cab is releasably secured to the drive frame at a pairof mounting posts carried on the drive frame.
 19. The mower of claim 18,wherein a roll over protection system is releasably secured to themounting posts on the drive frame in place of the cab when the mowerunit is used with the drive unit in place of the tracked unit.
 20. Themower of claim 1, wherein either the mower frame or the track frame isreleasably secured to the drive frame to releasably fix either the mowerframe or the track frame in a rigid manner to the drive frame wheneither the mower unit or the tracked unit is used with the drive unit.21. The mower of claim 20, further including an upwardly and rearwardlyextending cab carried on the track frame for enclosing the operator'sstation on the drive frame when the tracked unit is used with the driveunit.
 22. The mower of claim 1, wherein the drive wheels can be drivenin forward and reverse and independently of one another to provide zeroradius turn capability for the drive unit.